Abstract: Four kinds of supported ionic liquid catalysts were prepared by encapsulation of ionic liquids within the nanocage of KIT-5 and were used in the synthesis of polyoxymethylene dimethyl ether (PODE_n) from dimethoxymethane and trioxane; the effects of conditional parameters on the conversion of trioxane and the selectivity to targeted PODE_3-5 were systematically investigated. The results show that the optimum reaction parameters for the synthesis of polyoxymethylene dimethyl ether were: reaction time of 2 h, 100 ℃, dimethoxymethane to trioxane molar ratio of 1.5, and catalyst content of 3%. Under the optimum conditions, the encapsulated catalysts are efficient in the synthesis of polyoxymethylene dimethyl ether, with a similar catalytic activity to the homogeneous counterparts. Moreover, the encapsulated catalysts can be reused several times without remarkable loss of activity and product selectivity, which makes it a promising catalyst for practical applications.